The invention relates to nuclear medicine, and more particularly relates to nuclear medicine studies of the patient's heart. In its most immediate sense, the invention relates to myocardial perfusion studies.
In a SPECT myocardial perfusion study, the diagnostician examines a nuclear medicine image of the patient's myocardium (heart muscle) to see which areas of the muscle take up a radioisotope which is introduced into the patient's bloodstream. If any region of the myocardium does not take up the radioisotope, this means that this region is not perfused by blood and that the tissue in this region is therefore dead. If, on the other hand, the region does take up the radioisotope but not to the same extent as other regions, that region is affected by arteriosclerotic disease.
Myocardial perfusion studies are always carried out on the patient's left ventricle (because of the importance of this muscle in pumping blood through the body). Thus, the object of all myocardial perfusion studies is to identify the precise location of any diseased or dead myocardial tissue of the left ventricle. In order to do this, it is conventional practice to reference the position of a tissue region to the long axis of the left ventricle.
At the present time, such a reference is inherently subjective because identification of the long axis of the patient's left ventricle requires a technician to use judgement. Thus, even studies conducted on the same patient by the same technician may not be exactly comparable with respect to each other. Automation of the process by which the long axis of the left ventricle is identified would therefore improve the diagnostic utility of a myocardial perfusion study.
Furthermore, existing software programs by which a technician identifies the location of the long axis of the left ventricle require that the technician devote substantial time to the identification process. This is disadvantageous and it would be an advantage if the technician could be relieved of this work and thereby freed up to attend to other tasks.
One object of the invention is to provide method and apparatus for automatically identifying the long axis of a patient's left ventricle, thereby increasing the diagnostic utility of a myocardial perfusion study and allowing the technician to perform other tasks.
Another object of the invention is, in general, to improve on known nuclear medicine equipment and methodology.
In accordance with the invention, the method and apparatus disclosed in the above-referenced parent patent application is used to computer-identify a specific organ, namely the myocardium in the patient's left ventricle, on the basis of SPECT projection data acquired during a nuclear medicine study. Then, transverse slices of the left ventricle are reconstructed. From these, a representative transverse slice of the patient's left ventricle is automatically identified. Then, a reorientation plane is computer-established to pass through the projection of the long axis of the representative transverse slice; it is assumed that the long axis of the left ventricle will intersect the identified reorientation plane.
Then, the computer is used to reslice, along the reorientation axis, a perpendicular slice of the patient's left ventricle. From this, the computer automatically determines an axis which is assumed to be the long axis of the patient's left ventricle.
Advantageously, the identification of the long axis of the left ventricle can be checked by reconstructing oblique slices of the patient's left ventricle along the long axis and verifying the coincidence of the centers of such slices.
Use of the invention makes it easier to compare the rest and stress studies. This is because use of the invention produces studies which are consistent and are therefore easier to register with each other.